To maintain utility lines, utility companies and contractors use trucks with lift equipment to reach overhead lines carrying various utilities. Frequently service vehicles are equipped with lift equipment that can hold and carry a person from street level to the utility line. This is accomplished by attaching a boom to the chassis of the vehicle. At the end of the boom, a bucket is attached into which a person can stand and be lifted by the boom to an overhead location. Non conductive liners are designed that can be inserted into the bucket and insulate the occupant from high voltage that is frequently near overhead utility lines. It can be appreciated that the use of such equipment can expose the worker on the lift equipment to high voltage sources that may be conducted through the chassis of the vehicle and its lift equipment possibly shocking or electrocuting the worker should the equipment come into contact with the voltage source. To preserve safety of line workers, safety guidelines and precautions have been established to insulate the worker from exposure to high voltage sources while using lift equipment. Standards have been established for vehicle mounted elevating and rotating devices. These are covered in the American National Standards Institute (ANSI) published standard A92.2-2001. In particular, sections 5.4.2.5 and 5.4.3.5 relate to the testing of insulating liners that are inserted into buckets designed for carrying workers in an aerial device. ANSI A92.2-2001 Section 5.4.2.5 pertains to the testing of liners for design, qualification and quality assurance during manufacture, while ANSI A92.2-2001 Section 5.4.3.5 pertains to the periodic testing of liners is use in the field.
Current standards dictate that testing of insulating liners be carried out in a conductive liquid. Typically water is used for this type of testing. Water tanks used to perform this type of testing are bulky and require large volumes of water. Testing the dielectric properties of a liner requires that both the inner and outer surfaces be submerged to within six inches of the top of the liner. It can be appreciated that the structure to support such a volume of water must be large and heavy. This creates issues of storage and portability and makes testing in the field cumbersome. The electrification of water also creates an electrical hazard should anything happen during the testing process that would allow the leakage or spillage of water while exposed to a high voltage. Because of its property as a fluid the voltage in the electrified water can be distributed to unintended areas if a spill or leak occurs. The danger of exposure to electricity is heightened if the earth where the test is performed is damp and capable of conducting the voltage from the testing process. Electric current can flow through the damp ground to persons performing the testing procedure. Wet testing also necessitates the disposal of large volumes of water containing residue from the liner that may be exposed to the elements and the grease and dirt associated with the climbing in and out of a line worker. The water may also contain foreign matter as a result of the performance of the testing procedure. This water is generally disposed of by draining into the ground or dumped into a storm drain. Many gallons of clean water are wasted and the environment exposed to possible contamination. It would be beneficial therefore, to have the ability to test the dielectric properties of insulating liners without the use of liquid.